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Cell Phone/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim is high above the ground in a hot air balloon. He is speaking on a cell phone. TIM: What? You're totally breaking up. Hang on. Tim reaches over his head and pulls a lever. This releases heat into his balloon and causes it to rise. He reaches the height where a robot, Moby, is in his own balloon. Moby's mechanical arm stretches over to Tim, and he hands Tim a letter. Tim reads from a typed letter. TIM: Dear Tim and Moby, how do cell phones work? From, Kachiri. Regular phones, or landlines, use a system of wires to connect calls. You can learn all about this in our Telephone movie. An animation shows several houses, with telephone lines connecting them. TIM: Cellular phones are different. Sure, they have a mouthpiece and an earpiece like the phone in your house. But they're more like sophisticated radios than telephones. An image shows an open flip phone. TIM: All cell-phone-enabled regions are divided up into a grid of hexagon-shaped cells, which are usually about 26 square kilometers each. Cell phones connect to radio towers called base stations that are at the center of each cell. An animation shows connected cells as Tim describes. A base station appears in each hexagon and emits radio waves. MOBY: Beep. TIM: Yeah, there might be dozens of base stations in your area. If you live in a big city, there might be hundreds. When you cross from one cell to another, your phone connects automatically to that new base station. An animation shows Tim's balloon drifting from one base station to another. When he passes over the halfway line, his phone connects to the second base station's radio signal. TIM: The network of cells allows you to keep talking, no matter where you travel. MOBY: Beep. An animation shows Tim and Moby's balloons crossing a border from one cell to another. TIM: Yep, there's a base station right there. A base station transmits and receives radio waves. A base station's tower is shown transmitting radio waves. TIM: Your phone transmits your voice on one radio frequency, or channel, and receives the voice of whoever you're talking to on another channel. An animation shows an open flip phone. Radio waves go toward and away from the phone to show reception and transmission on different channels. TIM: When combined, these channels are together known as a duplex system, and it lets you and the person you're calling talk at the same time, not that that's always a good thing. Side-by-side animations show two girls talking on cell phones. Their channels cross as they speak and listen. TIM: All this stuff is monitored by something called a Mobile Telephone Switching Office, or MTSO. There's one in every area with cellular service. Each MTSO contains a sophisticated computer that's connected to all the base stations in the area. An image shows an MTSO, an office building connected by wires to a number of base stations. On top of the building is a single, tall antenna. TIM: When your phone contacts a base station, the base station contacts the MTSO. An animation shows a cell phone transmitting a signal to a base station, which transmits the signal to the MTSO. TIM: And the MTSO puts you through to whoever you're calling, whether you're calling a landline or another cell phone. A signal is broadcast from the antenna on top of the Mobile Telephone Switching Office. TIM: Cell phones are pretty high tech, but they don't actually have much power. They don't really need it, since they only need to send and receive as far as the nearest base station. And it’s a good thing, because it lets cell phones run on small batteries. An animation shows a cell phone communicating with a nearby base station. A small cell phone battery appears. TIM: Still, the low power can cause signal disruptions if you drive through a tunnel or try to talk from your basement. Images show a tunnel and a basement. MOBY: Beep. Moby waves to Tim from his hot air balloon. TIM: Nah. Cell phones really haven't been around for that long. The whole system depends on those cellular towers. Before that, mobile phones were kind of like, well, sort of like mobile radio transmitters. The two-way radios used in police cars and taxis and the field phones used by the Army in World War II were both ancestors of today's mobile phones. Images show a dashboard two-way radio and a military backpack radio. TIM: They were pretty big and clunky. You couldn't just slip one in your pocket. Moby holds a large field phone in one hand and its handset in the other. MOBY: Beep. TIM: The first cellular base stations started going up after World War II. But if you had a mobile phone, you had to stay inside the area covered by one cell. If you moved outside that area, your conversation was over. An image shows a hexagon cell with a base station and a cell phone. The base station is transmitting a signal to the cell phone. When the cell phone moves to another cell, the signal stops. TIM: The first modern cell networks went up in Japan and Scandinavia in the late 1970s and early 1980s. A map of the world shows Godzilla in Japan and a Viking in Scandinavia, both talking on a cell phone. TIM: When they proved successful, cell networks started popping up all over the world. The world map shows cell towers on every continent. TIM: Those early cell phones were something else. They weighed about 900 grams, cost $4,000 dollars, and provided a half-hour of talk time. An image shows a teen holding a large, early-model cell phone. MOBY: Beep. TIM: Well, a lot of electronic technology was pretty primitive back then. Images show an early game console, an early top-loading VCR, and an early computer. TIM: Like computers, over the past 25 years, cell phones have gotten smaller, more sophisticated, more powerful, and less expensive. Moby reaches for the cell phone that Tim is holding. MOBY: Beep. TIM: Why? Who do you need to call? MOBY: Beep. TIM: Fine, don't tell me. I'll just keep the phone. Tim holds the phone out of Moby's reach. Moby reaches above Tim's head and pulls the hot air balloon's lever. Tim's balloon shoots upward. TIM: Yaaah! Category:BrainPOP Transcripts Category:BrainPOP Engineering & Technology Transcripts